linux-ext4 - Re: High CPU Utilization When Copying to Ext4

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Message-ID: <20110708182425.GC3331@thunk.org>
Date:	Fri, 8 Jul 2011 14:24:25 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Sean McCauliff <Sean.D.McCauliff@...a.gov>
Cc:	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: High CPU Utilization When Copying to Ext4

OK, #1, can you try doing an experiment with "cp -r <src-path>
<dest-path>", and tell me whether the copy speed is faster or slower,
and whether the CPU utilization is faster or slower?  Even if it's a
bit slower to use cp -r, it will be easier for us to try to reproduce
things and to understand what cp -r is doing as opposed to some
mystery java program.

#2, if you know how to set up ftrace, can you enable the
ext4_mballoc_alloc tracepoint and send me a sample output (a few
hundred lines will be plenty).

The short version is basically:

<start your java copy program>
echo 1 > /sys/kernel/debug/tracing/events/ext4/ext4_mballoc_alloc/enable
<wait 30 seconds>
cat /sys/kernel/debug/tracing/trace > /var/tmp/trace-save
echo 0 > /sys/kernel/debug/tracing/events/ext4/ext4_mballoc_alloc/enable

						- Ted
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